Please enable JavaScript.
Coggle requires JavaScript to display documents.
Forces (speed (typical values: (walking 1.5 m/s
running 3 m/s
6 m/s),…
Forces
speed
-
the speed of a moving object is rarely constant. When people walk, run or travel in a car their speed is constantly changing
the speed of which a person can walk, run or cycle depends on many factors including: age, terrain, fitness and distance travelled
typical values:
- walking 1.5 m/s
- running 3 m/s
- 6 m/s
it is not only moving objects that have varying speed. The speed of sound and the speed of the wind also vary
-
for an object moving at a constant speed the distance travelled in a specific time can be calculated using the equation
distance travelled = speed x time
Acceleration
-
-
-
-
equation for uniform acceleration:
(final velocity)^2 - (initial velocity)^2 = 2 x acceleration x distance
near the earth's surface any object falling freely under gravity has an acceleration of amount 9.8m/s
an object falling through a fluid initially accelerates due to the force of gravity. Eventually the resultant force will be zero and the object will move at its terminal velocity
Gravity
weight is the force acting on an object due to gravity. The force of gravity close to the Earth is due to the gravitational field around the Earth
the weight of an object depends on the gravitational field strength at the point where the object is.
-
the weight of an object may be considered to act at a single point referred to as the object's 'centre of mass'
-
-
-
-
-
forces and elasticity
the extension of an elastic object, such as a spring, is directly proportional to the force applied, provided that the limit of proportionality is not exceeded
-
a force that stretches (or compresses) a spring does work and elastic potential energy is stored in the spring. Provided the spring is not inelastically deformed, the work done on the spring and the elastic potential energy stored are equal
-
Scalar vector quantities
-
-
a vector quantity may be represented by an arrow. The length of the arrow represents the magnitude and the direction of the arrow represents the direction of the vector quantity
Newtons laws
Newton's first law
if the resultant force acting on an object is zero and:
- the object is stationary, the object remains stationary
- the object is moving, the object continues to move at the same speed and in the same direction. So the object continues to move at the same velocity
-
so the velocity (speed and/or direction) of an object will only change if a resultant force is acting on the object
-
Newton's second law
the acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object
-
-
-
Newton's third law
whenever two objects interact, the forces they exert on each other are equal and opposite
Momentum
-
in a closed system, the total momentum before an event is equal to the total momentum after the event
-
Resultant forces
a number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together. This single force is called the resultant force
a single force can be resolved into two components acting nat right angles to each other. The two component forces together have the same effect as the single force
-
-
Reaction time
-
a drivers reaction time can be affected by tiredness, drugs, alcohol, distractions may also affect a driver's ability to react
-
stopping distance
the stopping distance of a vehicle is the sum of the distance the vehicle travels during the driver's reaction time and the distance it travels under the breaking force. For a given braking force the greater the speed of the vehicle, the greater the stopping distance